This invention relates to a novel emulsifier composition which exerts excellent improvement effects to starch containing food.
Due to its function and safety, mono- or diglyceride is widely used as emulsifier in the present food processing industry, and its function differs depending on the purity, appearance, physical and chemical properties, and the types of fatty acid that constitute the emulsifier.
In the case of starch containing food, such emulsifiers are required to react well, particularly with starch, to obtain a complex with the starch. Saturated fatty acid monoglyceride having 14 to 18 carbon atoms and of a high purity distilled monoglyceride is known to meet this requirement.
In the case of using mono- and diglyceride in the fat phase, there is no restriction on the physical properties of the mono- and diglyceride because they can be dissolved into fat. However, in case of starch-containing food, it is desirable to use mono- and diglyceride in the aqueous phase in order to obtain a starch-complexing improvement effect.
In these circumstances or where the emulsifier is mixed with the raw material in powdered form, physical appearance, physical and chemical properties and surface condition have a significant bearing on this function.
Monoglyceride is known to be polymorphic and is classified according to sub-.alpha., .alpha., .beta. and .beta.-crystalline forms which are arranged in order of increasing melting points. The .beta.-crystalline form is the most stable thermodynamically and monoglyceride has always been marketed in the .beta.-crystalline form.
The reason why the .alpha.-crystalline form is more effective in the aqueous phase can be assumed to be because of a difference in hydrophilicity. As a means of obtaining the .alpha.-crystalline form, there is a so-called conjoined crystal method employing the combined use of saturated fatty acid monoglyceride and fatty acid propyleneglycol ester (J. Am. Oil., Chem. 40, 725, (1963)); or a method wherein a dispersion in water is formed at a temperature below the melting point of monoglyceride. However, each of these methods have disadvantages, such as a small content of monoglyceride, difficulty in temperature control or in preservation properties.
From these standpoints, it would be advantageous to obtain a monoglyceride having the stable .beta.-crystalline form while, at the same time, exhibiting good functional properties. Various methods have been considered as means for improving the hydrophilic properties. In order to increase the surface area of crystals, there is a method whereby minute crystals were obtained by recrystallization using a solvent (Patent: TOKU-KOSHO No. 50-34613) and a method whereby an aqueous dispersion of the .beta.-crystalline form was obtained by adding a stabilizer into a dispersion or a method whereby a dry powdered monoglyceride was obtained by adding binders into a dispersion (Patent TOKU-KO-SHO No. 44-26900).
Each of these methods have excellent improvement effects. However, with respect to obtaining powdered monoglyceride, the methods were disadvantageous because they tended to be expensive from the standpoint of production efficiency, and a product in paste form proved to be inferior in handling, preservation and stability. Therefore, the development of a more simplified process has long been desired for obtaining a powdered monoglyceride which is effective in the aqueous phase. As a result of intensive research work in consideration of these shortcomings, the present inventors discovered a novel emulsifier composition which provides good quality improvement effects to starch containing food, and which is easier to handle, less expensive, withstands longer preservation time and is stable. This prior invention, of which the present invention is an improvement, is described in co-pending application Ser. No. 107,914.
As described in their copending application, the present inventors discovered that the expected purpose could be achieved by powdering an emulsifier composition comprising a high purity distilled monoglyceride composed of 65-85% of saturated fatty acid monoglyceride and 35-15% of unsaturated fatty acid monoglyceride, and having an iodine value of 10-40, and tempering the powdered composition for more than 30 minutes at a temperature of more than 45.degree. C. and which does not cause melting of the composition. In the composition, the number of carbon atoms for the saturated fatty acid is in the range of 12-22, and that for the unsaturated fatty acid is in the range of 16-22.
The composition can be produced either by using a fatty acid material (i.e., fat and oil) which fulfills the above requirements, or by using 2 or more different kinds of fatty acid monoglycerides.
If the amount of unsaturated fatty acid monoglyceride is less than 15% and the iodine value is less than 10, the expected results are not obtained. Likewise, if the amount is more than 35% and the iodine value is more than 40, the complex-forming ability with starch is deteriorated and, at the same time, it is difficult to obtain the composition in powdered form.
It was found that, by tempering the emulsifier composition thus obtained for more than 30 minutes at a temperature which is within the range of from more than 45.degree. C. to a temperature which does not melt the composition, the properties of the composition are improved drastically and the preservation stability is also improved. If the tempering temperature is below 45.degree. C., it takes longer to attain the required properties and the crystal sizes become coarse. Therefore, a lower temperature cannot satisfy both the production and expected property requirements.
When fatty acid monoglyceride is solidified by cooling, it forms the stable .beta.-crystalline form after undergoing successive crystal formation, from each of. sub-.alpha., .alpha. and .beta.' forms. But as the transition time becomes longer, the crystals thus obtained become coarser. Therefore, it is necessary to finish the transition as rapidly as possible in order to obtain minutely sized crystals in order to meet the purpose of the invention. The most effective method is to use solvent. The use of a solvent such as water or alcohol had already been proposed and reduced to practice at present.
However, as indicated earlier, problems lay in handling and preservation stability.
The inventors discovered that, from these standpoints, monoglyceride having unsaturated fatty acids with cis coordination in its double bond position suited the purpose of the invention.
As indicated earlier, the suitable percentages of saturated fatty acid monoglyceride and of unsaturated fatty acid monoglyceride are 65-85% for the former and 35-15% for the latter. From the standpoint of complex forming ability with starch, it is more advantageous to have as high a content of saturated fatty monoglyceride as possible in the mix for the improvement of functional properties.
Depending on the types of fatty acids, fatty acid monoglyceride has different polymorphic melting points. But, for a difference in number of carbon atoms within 4, it forms a solid solution. Therefore, it can be handled behaviorally as one fatty acid monoglyceride.
As the first stage in the production of the composition, the mix-melted fatty acid monoglyceride is cooled to a temperature below the sub-.alpha. crystal melting point and, more desirably, to below 35.degree. C. in normal cases. In this instance, unsaturated fatty acid monoglyceride, which is a minor constituent, can be solidified among crystals of saturated fatty acid monoglyceride. The second stage of production is a crystal transition stage produced by tempering. The tempering temperature is deisred to be above the crystal melting point of sub-.alpha. or .alpha. crystalline forms of saturated fatty acid monoglyceride, which is in a solid solution stage. This tempering process melts unsaturated fatty acid monoglyceride and saturated fatty acid monoglyceride crystallizes in a minute form and stabilizes. In this case, the appropriate degree of tempering and the solvent effect of the unsaturated fatty acid monoglyceride accelerate the transition of crystal to .beta.-crystalline form. Normal tempering is 2-8 days at 45.degree. C. and 30 minutes to one day at 50.degree.-55.degree. C.
The third stage of the process is cooling of the tempered monoglyceride. The product obtained has excellent properties and is stable for a long period of time.
Among the compositions disclosed in the above-described invention, fatty acid monoglyceride, which is composed of cis type unsaturated fatty acids is, on one hand, a good solvent and is compatible with saturated fatty acid monoglyceride, but the compatibility is not high and does not inhibit crystallization at a low temperature. On the other hand, it is largely hydrophilic even at a low temperature. Therefore, among saturated fatty acid monoglyceride, unsaturated fatty acid monoglyceride, when added with water, serves as a disintegrator and disperses saturated fatty acid monoglyceride in the aqueous phase. Monoglyceride which is composed of trans type unsaturated fatty acids is, due to its structure, largely compatible with saturated fatty acid monoglyceride and is believed to form a condition which is close to the solid solution state and its melting point is high. Therefore, this cannot be treated in the same manner as that of the cis type.
Furthermore, the purpose of the above-described invention is fulfilled to a large degree by the combined use of the substances described below. I.e., an emulsifier composition having good properties can be obtained by powdering a composition which is composed of the said monoglyceride composition mix-melted with less than 5% of a member selected from the group consisting of alcohols, organic acids, lecithin and stearoyl lacrylate which are compatible with fatty acid monoglyceride and by tempering or not tempering for more than 30 minutes at a temperature which is more than 45.degree. C., but which does not melt the said composition.
The additional substance, as a result of acting thermodynamically, helps to refine crystals of saturated fatty acid monoglyceride and to form a thin film of unsaturated fatty acid monoglyceride so that it can fulfill the purpose of the invention without tempering. Tempering also serves to improve the properties.
Alcohols which can be used include propylene glycol and glycerol. Organic acids can be selected from citric acid, malic acid, fumaric acid, succinic acid, glutamic acid, tartaric acid and lactic acid. Soy bean lecithin and egg yolk lecithin can be used as lecithin and lactylic stearate, sodium stearoyl-2-lactylate and calcium stearoyl-2-lactylate can be used as the stearoyl lactylate.
The emulsifier composition thus obtained exerts prominent effects. But, since the product is made structurally of saturated fatty acid monoglyceride, the crystal surface of which is surrounded by a thin film of unsaturated fatty acid monoglyceride, there sometimes arises problems such as caking or stickiness which develops on the surface of handling equipment under preservation and distribution environments at certain temperatures.
In order to overcome these shortcomings and as a result of devoted research work, the present inventors discovered a way to solve these problems by including, in the emulsifier composition described above and prepared according to the description of the co-pending application, 5-20% of fat that has a melting point which is more than the tempering temperature of the monoglyceride composition.